A conventional lathe machine generally includes a bed, a headstock that is mounted on the bed and that has a chuck rotatably holding a workpiece, a turret that is movably mounted on the bed and installed with different types of machining tools for processing the workpiece, a motor that drives the turret to move, a tailstock that is movably mounted on the bed and separably engaged with the turret, and a deep-hole drilling tool that is installed on the tailstock to operate deep-hole drilling on the workpiece.
Due to such structure of the conventional lathe machine, an operator must activate the motor to move the turret, then engage the turret with the tailstock, and drag the tailstock exactly to a desired position for an electrically-controlled deep-hole drilling operation on the workpiece, in which the turret serves as nothing more than a part of mechanical transmission for moving the tailstock. Moreover, due to a vibration caused by collision between the deep-hole drilling tool and the workpiece during the operation of the conventional lathe machine, the engagement between the turret and the tailstock may be loosened to form a backlash therebetween, thereby affecting operational accuracy of the conventional lathe machine.